Journal of Urban Environmental Management

Abstract In the present study, extraction of lithium from salts obtained from brine desalination in Gohar Zamin iron ore mine (Sirjan) was investigated using D2EHPA extractant solvent and kerosene diluent. This laboratory-scale study included 29 sets of experiments using a solvent extraction system. To perform the desired extraction experiments, equal volumes of the aqueous phase (10 ml) were contacted with the organic phase (D2EHPA + kerosene) at a specified concentration and then subjected to stirring in a magnetic stirrer for 30, 45, and 60 minutes at laboratory temperature (23 °C). In this investigation, was utilized form Box-Behnken (response surface design) to optimize and assessment of main variables influence of solvent extraction process such as pH, organic to aqueous phase ratio, stirring time, and D2EHPA percentage on lithium recovery. The linear interference model (2FI vs Linear) was applied as the response for lithium recovery. The accuracy and validity from this model were evaluated using variance analysis (ANOVA). According to the process results, optimal operating conditions for lithium recovery were 69.81% at condition of volume of D2EHPA extractant of 29.2%, pH of 5.6, organic to aqueous phase ratio 3:1, and 52.05 min stirring time. The results illustrated that the stirring time had a smaller effect than the two variables of extractant amount and ratio of O/A. The organic to aqueous phase ratio index O/A was more effective than other parameters on lithium recovery.

Abstract Surface silty sand soils, as a typical category of weak geotechnical materials, present major challenges in road engineering and environmental management due to their low shear strength, high susceptibility to erosion, and strong potential for dust release. This study aimed to evaluate the effect of styrene–acrylic copolymer on improving the physical and mechanical properties of these soils. Soil samples were prepared with three additive levels (2.5, 5, and 7.5% by dry weight). Standard Proctor compaction, Atterberg limits, and linear shrinkage tests were performed, followed by unconfined compressive strength (UCS) and California bearing ratio (CBR) tests after 7- and 21-day curing periods. Polymer addition slightly reduced maximum dry density from 1.79 g/cm³ (control) to 1.72–1.77 g/cm³, while optimum moisture content increased from 8% to 8.5–9.6%. The liquid limit increased from 20% to 21–23% and the plastic limit from 12% to 13–14%, with a nearly constant plasticity index (8–9%). After 21 days, UCS values reached 1.18, 1.64, and 2.03 MPa for soils with 2.5, 5, and 7.5% polymer, respectively, compared to 0.79 MPa for the untreated soil. Similarly, CBR values rose from 7.8% (control) to 11.2%, 15%, and 18.5%. Based on these results, the 7.5% dosage after 21 days is recommended as the optimum treatment, providing significant improvements in strength and bearing capacity, while simultaneously mitigating road dust emissions. Overall, the findings demonstrate the potential of styrene–acrylic polymer as an effective and sustainable solution for stabilizing weak silty sand soils.

Abstract This study investigates the pollution and sources of heavy metals in the soils and sediments of the tailings dam at the Chah-Gonbad copper mine. For this purpose, six sediment samples from the tailings dam and nine soil samples from its surroundings were collected and analyzed. The concentrations of pollutants including barium, cobalt, molybdenum, nickel, and vanadium were measured using a four-acid digestion method and inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the average concentrations of barium, cobalt, molybdenum, nickel, and vanadium in the tailings sediments were 585, 22, 3.7, 30.1, and 79.8 mg/kg, respectively, and in the surrounding soils were 244.8, 17, 0.63, 30.6, and 124.7 mg/kg, respectively. In contrast, cobalt was classified into classes 0 and 1, indicating either no pollution or slight pollution. Furthermore, vanadium and nickel were categorized in classes 1 and 2, suggesting slight to moderate pollution of these elements in some parts of the area. The findings of this study revealed that the weathering of parent rocks is the primary source of heavy metal concentrations in the area, but mining activities, particularly in the tailings sediments, have contributed to localized increases in the concentrations of some elements, including vanadium and nickel. These results emphasize the importance of continuous pollution monitoring and environmental management, including sediment stabilization and the use of pollution-reduction methods in the region.

Abstract The location of city service units such as fire stations in urban areas is always one of the issues of municipalities that should be investigated and determined very carefully. The effectiveness of service quality and efficiency of fire stations is highly dependent on their proper location. Therefore, in this study, an attempt is made to determine the appropriate place to use for the establishment of a fire station by examining location information in district 16 of Tehran municipality (Nazi Abad district). For this purpose, 8 indicators affecting the location of the station were determined. The Fuzzy Analytic Hierarchy Process was used in order to prioritize them and determine the weight of their effect. Then spatial information of each of the indicators for the studied area were prepared in ARCGIS and discussed. Finally, by combining the maps, suitable places to establish a fire station with maximum efficiency were determined. According to the results, the southern strip and a part of the northern area of the investigated area are completely suitable for building a fire station. There is no possibility to build a fire station in the northwest and west side of the area due to its usage. Also, the eastern and northeastern sides have a similar situation.